Apparatus for telephone-switchboards.



PATENTED JUNE 7, 1904.

'0. E. SGRI'BNER. APPARATUS FOR TELEPHONE SWITGHBOARDS.

APPLICATION FILED we. 17, 18957 NO MODEL.

mm mz ll irwssasx UNITED STATES Patented June '7, 1 904.

PATENT OFFICE.

CHARLES E. SCRIBNER, OF CHICAGO, ILLINOIS, ASSIGNOR TO WESTERN ELECTRIC COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

APPARATUS FOR TELEPHON 'E-SWITCHBOARDS.

SPECIFICATION forming part of Letters Patent No. 761,852, dated. June *7, 1904.

Application filed August 17,1895.

To aZZ whom it may concern:

Be it known that I, CHARLES E. SoRIBNER, a citizen of the United States, residing at Chicago, in the county ofCook and State of Illi- 5 nois, have invented a certain new and useful Improvement in Apparatus for Telephone- Switchboards, of which the following is a full, clear, concise, and exact description, refer:- ence being had to the accompanying drawings, forming a part of this specification.

My invention is a device for use in a telephone-switchboard for transmitting signaling or calling currents from the central station to the substation.

It consists in a secondary source of current adapted to operate the substation call-bell included in the circuit of the line at the central oflice, a calling-key associated with the plug-circuit, and a device in a local circuit controlled by said calling-key for rendering the secondary source of calling-current active to transmit calling-currents over the line.

In the preferred form of my invention I provide a repeating-coil or transformer in association with the telephone-line at the central ofiice, one of the helices of said transformer being included in the line-circuit and the other in a local circuit established by registering contacts of the plug and spring-jack, which local circuit may be temporarily completed by the calling-key through a generator of alternating or pulsatory currents.

Myinvention is particularly useful in connection with telephone-circuits which are per- 3 5 manently closed at the central station. In lines with suchv circuit connections, particu-. larly if the instrumentsat the central station be of low resistance, a large proportion of the signaling-current may be diverted from the telephone-line through these instruments, and the/operation of the substation-bell may be interfered with or prevented. In such cases my invention contemplates the inclusion of one helix of the transformer serially 45 in the line-circuit and the provision of a separate. local circuit including the other helix, into which the source of signaling-current may be introduced, whereby the signalingonly by the use of low-resistance impedance- .with those of my earlier application referred Serial No. 559,628. (No model.)

current is compelled to find its natural circuit through the-bridges or branches, and the 5d harmful effect of these is avoided. A switchboard system of this type is illustrated and described in a patent granted to me June 30, 1896, No. 563,07 3. The line-signalis asmall incandescent lamp, which is included in a ground branch containing a battery, together with an impedance-coil or inductive resistance. The usual plug-circuits for making connections between different lines by means of their spring-jacks are furnished, and other signal-lamps are associated with terminal plugs of the plug-circuit, one signal-lamp for each plug. In this system the greatest economy of operation of the signals is attained coils in the bridges or ground branches containing the lamp-signals and of high-resistance signal-bells at the substations. Hence the difiiculty which I have mentioned becomes important, and the application of my present invention is of peculiar advantage. In combining these two devices I may use the secondary helix of the induction-coil of my present invention as the impedance-coil of my earlier invention. I include the primary helix of the same induction-coil in a local circuit, including a generator of signaling-current, which is normally interrupted at two points namely, between registering contact-pieces of the spring-jacks and of the terminal plugs of the plug-circuits and between the switchcontacts of a calling-key in the plug-circuit. This latter key is constructed to interrupt the plug-circuit also during the transmission of a signal, so that the signaling-current is not diverted through the plug-circuit to produce false signals in the call-initiating line.

The accompanying diagram shows the circuits of my present invention in combination to. Two substations A and B are represented, connected by line-wires, with switching and signaling apparatus at the central station C. At the substation a receiving-telephone a and a transmitting-telephone a are included sorially in one branch from the line conductor 1 and a signal-bell u" in another branch from the same conductor. The lever of the telephone switch-hook a constitutes a circuit-terminal of the line conductor 2 and serves to switch the telephonic and the signaling appliances alternately into the line. The receiving-telephone a may be of twenty-five ohms resistance, and the transmittin g-tele 'ihone may have a normal quiescent resistance of one lumdred or two hundred ohms. The bell a should have a high resistance, five thousand ohms being a suitable amount. The line conductor 1 extends to two spring-jacks b and on two difl'erent sections 0 and a of a multiple switchboard. Itis continued through a signal-lamp (Z on section 0, associated with spring-jack 7/, and through the helix 0 of the transformer e and thence to earth through a battery f, which may be common to the different lines of the exchange. Line conductorZis connected with other contact-points in the same spring-jacks and is led through an impedance-coil g to earth. Battery f is thus in a bridge of the telephone-line, said bridge including the signal-lamp (Z and helix 0 of the transformer on one side of the battery and the impedancecoil 9 on the other side thereof. The coil 7 and the helix 0 may have approximatel y equal resistances and impedances for the purpose of maintaining the static balance of the line-circuits as to telephonic currents. should be of such electromotive force that the normal current flowing out through conductor 1, hell (1?, at the substation and returning through line 2 shall be insuflicient to illuminate the lamp (fl. \Yhen, however, the circuit is completed at the substation through the telephones, the high resistance of the bell will be cut outof the circuitand thelamp (X will be lighted. On each spring-jack of the line is a tubular thimble /l, which is presented at the front of the spring-jack in order that it may serve as a test-ring. The different rings 71. are connected with wire 3. which includes the primary helix of transformer L and extends to one pole of the generator I of signaling-current. The usual plug-circuitformed by link conductors t 5, terminating in loop-plugs Z' and 71:, is provided for switching the lines into connection with each other by means of their spring-jacks. Three contactpieces (desig nated Z, Z, and Z respectively) of the plug register with the two line-springs and with'the test-ring a of a spring-jack into which the plug is inserted. Contacts/ and /of theplugs l;- and 7: form the terminals of the conductors 4and 50f the plug-circuit. respectively. The conductor t includes serially two helices of the transformer m and is grounded at a point intermediate of the helices. The other conductor 5 of theplugcircuit includes serially the other two windings of the transformer or induction-coil and also includes the supervisory signal-lamps w a, said lamps being interposed serially in said conductor between the Battery f two last-mentioned windings of the induction-coil. The free pole of the batteryf is connected with said conductor at a point between the two supervisory signal-lamps u, and so between the two windings of that half of the induction-coil which is serially included in the conductor Signal-hunps and w are shunted by resistance-coils u and o and a battery 7). This last device forms an important feature of my Patent No. 503,073, referred to, and is fully described in the specilication. .I may mention here, however, that battery is of such strength as to illuminate lamps n and 1/ through their resistances r) and 0 while the plug-circuit is incomplete; but it is so adjusted with respect to battery f that when this circuit is completed by the removal of the substation telephone of a line with which the plug-circuit may be connected the current of battery 1) is diverted from lamps u and 11, leaving them dark. llence either of these lamps becomes lighted or dark as the telephone of the line with which the corresponding plug Z or X" may be connected is removed from or replaced upon its switch-hook. The lamps thus serve to indicate the condition of use or disuse of the apparatus at the. dill'erent stations of two connected lines.

The operator is furnished with the usual telephone set and key w for controlling its connection with the cord-circuiti The center of the magnet-coil of the receiving-telephone is grounded for testing purposes in the usual way. In each plug-circuit is a callingkey for transmitting a signaling-current through plug Z to the substation of the line with which this plug is connected to operate the bell there. This key has three switchsprings s, s and a, each having a normal resting contact. The comluctors i, 5, and (3 include the resting anvils and switch-springs of this key in the orderv named. \Yhen the key is manipulated, the switch-springs are separated from their anvils, the crmductors l, 5, and (5 being thereby interrupted, and the spring A is closed to its alternate contactpoint a, which constitutes a terminal of generator of signaling-current.

The mode of operation of the line-signals and the supervisory signals 11 and n preliminary to and during the existence of connection between lines has, I believe, been sulliciently described. 1 will therefore pass to that stage of the process of cmmectingdines which involves my present invention that is, when having answered the call from line at station A, for example, the operator inserts plug Z" into the spring-jack 0" of line to station B to transmit a signaling-current to the bell at that station. The depression or mani pulation of key a interrupts the connection of plug Z" with the remainder of the plug-circuit and closes the contact-piece which now registers with the ring of the spring-jack 6* against the anvil s'.

A local circuit from generator; is thus completed through conground branches at the central station instead of being shunted from the line-circuit, as in the system commonly employed.

For the purpose of producing a suitable busy test for the multiple switchboard I have made use of conductor 6 and test-rings 71, with their associated circuits. A grounded batteryt is connected with conductor 6, so that from the moment a plug is inserted into any spring-jack of a line the test-rings it of the line are electrified to a difierenceof potential from earth. The operator requiring information as to the condition of the line may test in the usual way by applying the tipZ of the plug 70 to the test-ring of the spring-jack, when, if the line be in use, a current will be produced through conductor'5, key 7" and one-half of the magnet-coil of the receiving-telephone to earth. An audible signal will then be caused in the telephone, which will indicatethat the line is already in use.

My invention is defined in the following claims:

1. The combination with two telephonelines and link conductors 4: 5 at a central office, and connection-switches is is of said link conductors, for temporarily uniting said lines in a complete telephone-circuit, the called line having a signal-bell at the substation, of

a line-battery, a signal-indicating device, and

a normally inactive source 0 of calling-current adapted to operate the substation callbell, permanently included in the circuit of the called line'independent of the telephonecircuit established by said link conductors, a local circuit established at the connectionswitch of the called line and including asource of current and a device 6', adapted to render said source 0 of calling-current active, and a calling-key having switch-contacts adapted to break the telephone-circuit between the lines and complete said local circuit, whereby the signal-bell at the called station is rung, substantially as described.

2. The combination with two telephonelines, each extending from a substation to a central oflice, one of said lines being a callingline and the other a called line, of a source of current, a line-signal and the secondary of an induction-coil permanently included in the circuit of each line at the central office, link conductors 4: 5, and connection-switches 7a is for uniting the lines at points between the induction-coil windings thereof and the respective substations, forming a through-circuit for telephonic communication between the substations, a signal-bell at the substation of the called line, a local circuit established at the connection-switch of the called line including a calling-generator and the primary of the induction-coil of that line, and a calling-key having contacts adapted to break the circuit of the link conductors and close said local circuit, whereby the signal-bell at the called station is operated, as set forth.

- 3. The combination with atelephone-line extending from a substation toa central office and a substation-switch controlling the circuit of said line, of a call-bell at the substation, two branches for the line at the central oflice,

one of said branches being permanently connected with the line, a secondary source of ringing-current included serially therein, together with a battery and a line-signal, a switch for making connection with the line through the other of said branches, said last-mentioned branch forming a portion of the talking-circuit of said line, anormally open local circuit containing means for rendering said secondary source of current active, and a key adaptedv when actuated to open said talking-circuit and close said local circuit.

4. The combination with a telephone-line extending froma substation to a line-signal and a battery at the central ofiice, of a substation-switch controlling the circuit of said line, asignal-bell atthe substation, asecondary source of ringing-current permanently. included in the line at the central office, a branch circuit adapted when completed to form a continuation of the telephonic circuit of said line, a connection-switch adapted to connect said branch with the line at a point between the said secondary source of ringing-current and the substation, a local circuit partially established by the closure of said connection-switch, including means for rendering said secondary source of current active, and a key adapted when actuated to open said branch circuit and complete said local circuit.

In witness whereof I hereunto subscribe my namethis 12th day of July, A. D. 1895.

CHARLES E. sonnsnnn.

Witnesses:

- ELLA EDLER,

MYRTA F. GREEN. 

